High-tension electrical power lines are seen at the Azura-Edo IPP on the outskirt of Benin City Thomson Reuters By Alexis Akwagyiram and Paul Carsten

LAGOS (Reuters) - Plans to build another privately-financed power station in Nigeria to help end decades of chronic blackouts have been delayed because of concerns about persistent shortfalls in payments for electricity across the sector.

The $1.1 billion Qua Iboe Power Plant being developed by energy infrastructure company Black Rhino and the state-owned Nigerian National Petroleum Corporation won't get a green light by the end of 2018 as planned and it was unclear when the deal might close, NNPC told Reuters.

The delay is a setback for Africa's biggest oil producer where 80 million people don't have access to grid power supplies and it exposes the difficulties in attracting private investment to a sector that successive governments have tried to reform.

The uncertainty surrounding the 540-megawatt Qua Iboe plant stems from the difficulties Nigeria's first privately-financed independent power project - the 460-megawatt Azura-Edo plant - has encountered since it came online this year.

Azura was meant to be a model for a string of independent power plants financed by international investors. To give them confidence to invest in the first major plant since the power sector was privatized in 2013, the World Bank provided a safeguard known as a partial risk guarantee - meaning the lender would step in if Nigeria defaulted on payments.

Under the current system, the government-owned Nigerian Bulk Electricity Trading company (NBET) buys power from generators and passes it on to distributors who then collect money from customers and reimburse NBET.

But because NBET is not paid in full for the power it buys, generators such as Azura have been partly reimbursed from an emergency central bank loan fund created to keep the sector afloat.

NNPC told Reuters one of the reasons the Qua Iboe plant (QIPP), which is due to be built in the southern state of Akwa Ibom, had been delayed was because NBET appeared reluctant to commit to new projects to avoid increasing its liabilities.

"The continued delay relates to the current cashflow challenges at NBET, as highlighted by the Azura project," a spokesman for NNPC said in an emailed statement. "This concern is justified by the fact that NBET is yet to see an improvement in collections from DISCOs (distribution companies)."

NBET did not immediately respond to a request for comment on NNPC's statement about QIPP.

NBET chief executive Marilyn Amobi told Reuters in November that it was hard for the company to work because of poor infrastructure and shortfalls in cash from distributors needed to reimburse generators.

"You don't have the infrastructure, you don't have the financial position to do it, you don't actually have the products, and you don't have the grid," she said.

WORLD BANK CONDITIONS

NNPC said another problem for QIPP was that the World Bank had made a partial risk guarantee, similar to the one that helped Azura attract investors, contingent on the government's implementation of an agreed power sector recovery plan.

"In theory it is okay, but the risk is there are delays in the approvals which may impact QIPP," NNPC said.

Power ministry officials and the World Bank have been in talks about long-term structural changes needed to trigger the release of a $1 billion loan to help pay for reforms.

A World Bank spokeswoman said the loan had yet to be submitted to its board for approval and that the Washington-based lender considered the recovery plan to be "critical for de-risking the sector for private investments".

Problems that need to be tackled include decaying infrastructure, mounting debts, low tariffs for electricity and a dilapidated government-owned grid that would collapse if all the country's power generators operated at full tilt.

Even though NBET has an agreement to buy 13 gigawatts (GW) from power generators, the system can only cope with distributors sending out an average of 4 GW, according to the ministry of power.

The World Bank spokeswoman confirmed any future guarantees for independent power plants (IPPs) would be linked to the plan's implementation - because the economic and financial viability of generation capacity expansion was at risk.

A spokeswoman for Black Rhino, which is one of private equity firm Blackstone's portfolio companies, declined to comment on NNPC's announcement of a delay to QIPP.

When the project was unveiled, Nigerian cement giant Dangote Group was named as a joint venture partner - along with Black Rhino and the Nigerian National Petroleum Corporation.

But a Dangote executive told Reuters on condition of anonymity that the company, owned by Africa's richest man, Aliko Dangote, had pulled out.

"The huge debt level, and, the fact the IPPs are not making profits, is another reason for prospective investors to be deterred," he said. "Further, collecting revenue from the distribution companies is also becoming a mirage."

A Dangote Group spokesman declined to comment on the delay to QIPP, or whether the company had pulled out.

'ILLIQUID AND INSOLVENT'

The payment problems in the Nigerian power sector were thrust into the spotlight in March when four generating companies filed a lawsuit against the government and Azura.

To ensure the generating companies were paid in full throughout 2017 and 2018, the government created a 701 billion naira ($2.3 billion) loan fund at the central bank to guarantee payments. When the fund was established in 2017, Azura wasn't part of the calculations.

But when Azura started producing electricity, the fund was also used to pay the new plant to ensure the terms of loan deals guaranteed by the World Bank were not breached. As a result, the other companies were told they would only receive 80 percent of the sums owed, according to the lawsuit filed in March.

The four energy companies want the fund to reimburse them in full, rather than allocating part of the money to the new plant.

Azura declined to comment on payments for power generated.

"If the central bank wasn't paying, the system would collapse," an official at a multilateral lender said on condition of anonymity. "Qua Iboe IPP would enter a system that is illiquid and insolvent. The liquidity is being provided by the central bank."

The official said QIPP would need the same partial risk guarantee Azura received to get off the ground, but the handling of payments to Azura by the Nigerian authorities so far meant there was little appetite to offer the same support.

Fola Fagbule, senior vice president and head of advisory at Africa Finance Corporation (AFC) - one of the multilateral lenders that invested in Azura - agreed that the Qua Iboe project would struggle without payment guarantees.

"What you have is an insolvent system," he said. "It is really difficult to make a case for a project on that scale."

A person with direct knowledge of QIPP who declined to be named said Azura's experience was damaging international investors' view of Nigeria, Africa's most populous nation.

"There has to be some understanding of how the sector is going to be able to afford new electrons coming into the grid," the person said. "(Those involved) do not want QIPP to build a project that could just end up in a default situation."

'KNOTTY ISSUES'

Nigeria's privatized power sector typically does not use meters to provide invoices, bill collections are low and energy tariffs have remained fixed for three years, meaning customers receive unsustainably cheap electricity.

The effect, say industry experts, is that electricity distribution companies recover so little revenue from customers that they pay less than a third of what they owe to generating companies - and that's why debts have ballooned.

Sunday Oduntan, spokesman for the Association of Nigerian Electricity Distributors, said debt levels in the sector were caused by the artificial suppression of tariffs. He said there was a 1.3 trillion naira ($4.2 billion) market shortfall that meant distributors were unable to invest in improvements.

"You cannot be selling a product below cost price and expect high remittance. The shortfall in the sector is because of the lack of a cost-reflective tariff," said Oduntan, who speaks on behalf of Nigeria's 11 electricity distribution companies.

Debts across the sector partly stem from a currency crisis that took hold in 2016, just months after Azura secured its financing. The bulk of power company costs are in U.S. dollars but customers pay for power in naira.

The naira lost about 30 percent of its value against the U.S. dollar in June 2016 but the devaluation was not factored into a government tariff structure that has remained unchanged.

Louis Edozien, permanent secretary in the ministry of power, told Reuters there was evidence tariffs must rise, but it was also the responsibility of distributors to improve their collections, partly through better metering and infrastructure.

As for the future of QIPP, the state oil company said it would take six to eight months from whenever NBET executes an agreement to purchase power from the plant before a final investment decision could be taken.

The NNPC spokesman said there were a number of other "knotty issues", including the completion of a transmission line from the project site. He said QIPP had now agreed in a major concession to pay $20 million for it to be finished.

He also said there was a disagreement between QIPP and the central bank about the exchange rate at which power producers could buy U.S. dollars with naira. He said this had been escalated to the minister of finance.

With the $1 billion World Bank power sector loan on hold for now, the government is considering putting another 600 billion naira into the central bank fund to pay generators when the initial amount runs out early next year, sources said.

It was not clear how the central bank loans to the sector would be repaid.

Central Bank Governor Godwin Emefiele told Reuters that payments from the fund could be made up to February and that the bank was holding talks with World Bank officials.

"The loan negotiations are still in progress with no terminal date yet fixed," the power ministry's Edozien said.

($1 = 306.6000 naira)

(Reporting by Alexis Akwagyiram and Paul Carsten; additional reporting by Camillus Eboh in Abuja, Chijioke Ohuocha in Lagos and Karin Strohecker in London; editing by David Clarke)